Stub for Listener class

This commit has stub for Listener class, which can be used to register
the events and handle the callback functionality for those events.
This commit only adds stub class for Listener.

Change-Id: I8731abc212239823e7062e3ee23f46a150b942a8
Signed-off-by: Anupama B R <anupama.b.r1@ibm.com>
diff --git a/vpd-manager/oem-handler/ibm_handler.cpp b/vpd-manager/oem-handler/ibm_handler.cpp
index 49fafe2..745fa57 100644
--- a/vpd-manager/oem-handler/ibm_handler.cpp
+++ b/vpd-manager/oem-handler/ibm_handler.cpp
@@ -63,6 +63,11 @@
     // set callback to detect any asset tag change
     registerAssetTagChangeCallback();
 
+    // Instantiate Listener object
+    // ToDo: listening assetTag and HostState properties will move under
+    // Listener class
+    m_eventListener = std::make_shared<Listener>(m_asioConnection);
+
     // set async timer to detect if system VPD is published on D-Bus.
     SetTimerToDetectSVPDOnDbus();